From: Bit Gossip (bit.gossip@chello.nl)
Date: Thu Aug 23 2007 - 06:19:28 ART
Experts,
in many practice-labsit is required to configure one of the Cat3550 as
multicast receiver for certain groups so that it replies to ping send to that
particular group. This is done using 'ip igmp join-group 224.224.224.224' but
to me this never works, see below.
If I configure only 'ip igmp join-group 224.224.224.224' I notice from
neighbor routers that the Cat3550 doesn't actually send any IGMP report for
the group.
So I enable 'ip multicast-routing' and 'ip sparse-mode' on the interface and
at this point IGMP reports are finally sent.
But still Cat3550 doesn't reply to ping complaing of not being able to RPF to
the RP, which makes sense because no RP has been defined. Actually I don't
want to define any RP on this switch because I want it to behave just like a
dumb host and not like a multicast router.
S4#ping 224.224.224.224
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.224.224.224, timeout is 2 seconds:
1d01h: IP(0): MAC sa=000b.464a.4180 (Vlan106), IP last-hop=10.1.68.10
1d01h: IP(0): IP tos=0x0, len=100, id=10, ttl=254, prot=1
1d01h: IP(0): s=10.1.68.10 (Vlan106) d=224.224.224.224 id=10, ttl=254, prot=1,
len=114(100), RPF lookup failed for source or RP.
I tried to put a static mroute but it doesn't fix the problem, so to make it
happy I configure itself as a dummy RP and finally it replies to the multicast
ping
S4#ping 224.224.224.224
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.224.224.224, timeout is 2 seconds:
Reply to request 0 from 10.1.68.10, 4 ms
An alternative to configuring a dummy RP is to configure the interface in
dense mode; this also works.
Is it really so complicated to convince this Cat 3550 to reply to the ping or
I am missing something?
What about Cat3560, I can not test it because I don't have it?
S4#show ver
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version
12.2(25)SEE3, RELEASE SOFTWARE (fc2)
This archive was generated by hypermail 2.1.4 : Sat Sep 01 2007 - 11:32:12 ART